The goal of this project is to address the question of the role played by norepinephrine in vasopressin release by the application of a new technique, used in concert with more established methods. This new technique is the method for the simultaneous visualization of monoamines and neuropeptides as developed by our laboratory. The more established methods are radioimmunoassay of vasopressin and microspectrofluorometry of monoamine histofluorescence. We plan on examining some of the unanswered questions concerning the applicability of our technique to functional and anatomical neuro-biological problems involving neuronal interactions, particularly between aminergic afferents and peptidergic target neurons. The neural circuit of brain stem norepinephrine pathways to vasopressin neurons of the hypothalamus has been chosen as a model in part because it can be tested both anatomically and physiologically. The functional output of this system will be measured with vasopressin radioimmunoassay, while the details of the anatomical degree of interaction will be assessed with our combined immunocytochemical-histofluorescence analysis. The project also will develop the use of a newly conceived instrument, the comparator bridge microspectrofluorometer as a tool for determining neuronal activity in identified neurons during a specific functional state.